Bombay high is a highly heterogeneous, multi-layered carbonate reservoir overlain by gascap and underlain by aquifer in Western continental shelf of India and is in mature stage of its producing life. The field is currently undergoing "Mid-life Crisis", necessitating major re-development and well interventions programs for stemming the decline in oil and gas production and maximization of recovery. Being an offshore field, sidetracking (LDST, MDST and SDST) of existing wells and drilling of infill wells through clamp-on have become sort of immediate preferred cost-effective option in Bombay High; firstly, for sustained oil production and commensurating the water injection and secondly for facilitating the additional recovery of bypassed, un-swept/less-depleted reserves. Failures/limited success of repetitive workover jobs, poor cementation, bad wellbore condition, early water breakthrough have made many wells susceptible to channeling behind casing and cross flow between the layers. Relocation of such wells and utilization of slot have become inevitable. Sidetracking is being practiced, as a measure for reducing the inventory of sick wells where all the conventional remedial measures have not met with desired results and have also limited the further scope of rectification. This paper deals with the selection criteria, implementation and analysis of techno-economic successes and failures of re-entry/re-engineering of sub-optimal/uneconomical and clamp-on infill wells and also summarizes what has been learnt over the past several years and future scope of such activities. INTRODUCTION The Bombay High Field located nearly 160 Km W-NW of Bombay (Now Known as Mumbai) city in Arabian Sea was discovered in 1974. The field holds 1724 MMt and 389 BCM of initial in-place oil and gas respectively. The field was put on commercial production in 1976. The field production peaked around 19.5 MMTA during 1984–85 and maintained the same production level for about 7 years. Thereafter production started declining and reached to the level of about 10MMTPA at present During last few years the field is engulfed by typical oil field problems like high water cut, high GOR, differential depletion, water breakthrough and aging of facilities. All out efforts are being made to arrest the decline through massive well intervention programs and also by drilling new infill development wells. Drilling of new infill wells by installing the clamp-on on the existing platforms where no free slots are available and also by sidetracking the problematic existing wells have been preferred to step up the production and to drain the bypassed oil. The present paper discusses about selection, implementation and success/failure of these two techniques practiced in the Bombay High field.
Importance of pressure transient analysis during preparation of development schemes and performance analysis of oil/gas reservoirs is accredited in oil and gas industry due to its usage in estimation of petrophysical parameters of the reservoir and analysis of inflow performance relationship of oil wells, open flow performance of gas wells etc .In general, data analysis may be stated as a two-fold process: (i) data management , se -l ection and calculations and (ii) plotting of the required data . Most of the available PC based software packages for pressure transient analysis perform complex calculations but are deficient in their data management / graphic output capabilities which usually is rigid and limited. Based on the popular spreadsheet software package Quattro ProTM , a powerful and timesaving spreadsheet program for pressure transient analysis is presented . The spreadsheet prepared is simple to use and can be customised to user's needs by modifying the given format with a provision of further expansion.
This paper was selected forMascmtatkm byqn SPE Program Committee follow"ngreview of informaUon containedIn an qbalract submitted by tie auhr(s),Conterda of tie papar, as pented, have not baa!? retiawed by U!e Society cd Petroleum Engineers qnd are subject to cc.madon by tie q h+),The matarial, qs pesanfed, does not necessarily mffecf any position of the Society of PetrOlaum Engineers, Ha ofticera, or membars. Papers pmserded qt SPE meetings we subject to pddicafica reviaw by Edltwkl Committees of the SOciefy of Pek4eum Engineers. Ele*Onic repfoducdon, cWrifsAiOn, or stcfage of any part of fiis papar fof commercial pposes Wmut the written ccmsentof me Society of Petroleum Engineers Is~ohitited. Permission to reproduce in @nt is residcted ta qn qbskacf of not more than 300 words; illustrationsmay not be coded. The qbstract musf contain ccmspicuws q cknowledgment of where and by whom tie paper was~sented. Write Ubmian, SPE, P,O, Box 833836, Richardson, TX 75083-3838, U.S.A, fas 01-972-952-9435. AbstractOilfield data fall in several categories. If one were to study the field behaviour from seismic data acquisition stage through simulation in light of the other, one would be confronted with the highly daunting task of studying some data in the light of other, another chunk in conjunction with yet another and so on. Leave aside the actual daa the database structure itself can run in hundreds of tables and yet remain incomplete. So the complexities involved are all too obvious. Every time database designs are looked upon from managerial points of view, and as they pass through ditlerent manager% a need to restructure them is felt. Difl?erent managers have different ways of looking at the data and difEerent corners on which to lay stress upon, Understandably, in a multidisciplinary environment, if one were satisfied with the outputs, other would only be partly satisfied while there may be someone not at all subscribing to the ideas. This is where a strong need to create junction to cross roads is felt. But the questions are i) Is it possible ? and ii) Is there a solution which respects all the disparities and brews them into a meaningful concoction ? This paper attempts at suggesting some solutions,
In heterogeneous stratified reservoirs with low vertical communication between the layers, the best results are normally achieved if the separate layers are produced with a separate set of Wells. However, in a commingled production with poor vertical sweep due to high permeable thief zones, an improved behavior of such a reservoir can be efficiently attained by controlling the injection and production rates of wells to reduce (or stop) injection in the thief zones, and/or production from high permeable layers with high water cut. Technically this can be done by recompletion of wells or with the application of gel technology. The problem high GOR & high water cut wells of Bombay High L-III reservoir can be classified into three categories:Wells producing high amount of gas &/or water due to hardware leak and flow behind casing. The unwanted gas/water production here is due to contribution from zones not opened/exposed for production.Wells producing from multiple layers and a single layer producing major amount of gas or water. The unwanted water production may be due to breakthrough of injection water in one or more high permeable layers. The unwanted gas production may be due to cusping.Wells where early breakthrough has occurred due to thin high permeability streaks in a sublayer between Injectors and Producers. Here, the treatment may involve treating a portion of sublayer. In the past several Chemical water shutoff jobs in Bombay High Field have resulted in failures. The job failure can mainly be attributed to high reservoir temperature and incompatibility of Gel system with reservoir rock. Gel systems were quite sensitive to variations in temperature and pH. Also cross flow in the well bore during shut in conditions was also an important reason in some cases. An improved polymer gel treatment has been successfully applied in Bombay High Field - a high temperature carbonate reservoir, to control excessive gas or water production and to modify the injection profiles. Ten Wells were treated as a pilot: 6 for Gas Control, 3 for Water Control and 1 for Injection Profile Improvement. All the planned wells exhibited at least one, usually more than one, of the following conditions: At least one interval with vuggy porosity, poor primary cement over at least a portion of pay, additional loss of rock volume due to acidization, reservoir pressure less than hydrostatic in producing wells, differential pressure between zones due to differential depletion or water flood support. This paper discusses in detail the lessons learnt from the job failures and the successes with the use of polymer gels in such harsh conditions of Bombay high field. Introduction Bombay High, a giant oil field discovered in 1974, is located 160 km offshore WestNorthwest of Mumbai in Arabian Sea. Hydrocarbons have been found in Limestone, clastic and basement in the intervals -905m to -1950m MSL. It has two main limestone reservoirs of Miocene age, namely L-II and L-III. L-II reservoir is hydrocarbon bearing in Bombay High North (BHN) and L-III is hydrocarbon bearing in both Bombay High North and Bombay High South (BHS). The hydrocarbon accumulation is largely controlled by the structure which is a broad North-South trending anticline with a large portion of the eastern limb truncated by the eastern boundary fault (Figure: 1). The L-III reservoir is multilayered with shale, limestone sequence and hold about 94% of the total initial oil in place and reserves. The northern and southern parts of Bombay High field are hydrodynamically separated by an East-West trending shale channel in L-III reservoir, with perceptible difference in gas-oil contact level in L-III, in the north and the south Bombay High1.
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